Down-hole fluid fuel burner



`une 7, 1966 F. M. SMITH DOWN-HOLE FLUID FUEL BURNER Filed DeC. 20, 1963 United States Patent O 3,254,721 DOWN-HOLE FLUID FUEL BURNER Francis M. Smith, Jefferson Township, Butler County, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware t Filed Dec. 20, 1963, Ser. No. 332,073 12 Claims. (Cl. 166-59) This invention relates to an apparatus for burning fluid fuels in a confined space at superatmospheric pressures to obtain high rates of heat release.

A device for generating heat in the bore hole of a well can serve a variety of purposes. For example, at temperatures in the range of from 250 to 400 F., it can be used to consolidate unconsolidated subterranean formations by a process of warm air coki-ng of the crude oil in the sand grains of the formation. At higher temperatures in .the ran-ge of from 400 to l000 F., the heating device can be used to initiate in situ combustion of the crude oil, lower oil viscosity, land decrease bore hole damage caused by clay swelling, emulsion blockage and paratn deposition.

Both electrical heaters and fluid fuel burners have been suggested for supplying heat to the bore hole of a'well penetrating a subterranean rock formation. The electrical heaters are subject to serious limitations in that they require heavy, large diameter electric cables to supply current to the heating apparatus, lare expensive to construct and operate, and are not capable of delivering heat at high rates. Previously suggested designs for -fiuid fuel burners are also subject to many disadvantages. Many such burners are not capable of providing large quantities of hea-t; the rate of heat release being of the order of 100,000 B.t.u.s per hour or less. Many fiuid fuel burners require complicated and expensive construction having large diameters which do not permit their use in confined spaces such as conventional oil well tubing. With the smaller fluid fuel burners, the maintenance of a continuous heat supply is difiicult because of the tendency to flame out resulting from the high velocity of fuel-air mixtures injected at highpressures through an enclosed space. Proper cont-rol of the heat output in fluid f'uel burners has been a continuous problem in the past, and many burner designs have not been practical because of the tendency to provide localized regions of very high temperature which burn through the tubing or iother portions of the well appara-tus.

This invention resides in a fluid fuel burner for use in the bore hole of 'a well in which a `fuel conduit opens into an elongated combustion tube through a closure at the inlet end of the tube. A plurality of passages open tangentially in a single direction through the side of the combustion tube downstream lfrom the end of the fuel conduit to provide a vortex of relatively cool air around the inner surface ofthe combustion tube. Another plurality of passages extend downwardly through the closure at the inlet end of the com'bustion tube to provide -a stream of ai-r to move a mixture of air and fuel downwardly through the combustion tube. The burner'apparatus also contains a sealing means near the outlet end of the combustion tube which forms a barrier within an annular air conduit around the burner apparatus and aids in forcing the flow of air from the air conduit through the passages into the combustion tube.

A more complete description of the improved down hole burner apparatus of the present invention is given with reference to the attached drawings in which:

. FIGURE 1 shows -a view, partially in vertical section, of the burner apparatus positioned in the bore hole of a well.

FIGURE 2 is an enlarged view, partially in vertical section, of a burner apparatus suspended in the bore hole of "ice a well and showing the internal construction of the burner.

FIGURE 3 is a cross 'section view taken along the line III-'III of FIGURE 2 and shows the tangential relationship of the tangential slots with the combustion chamber of the burner.

FIGURE 4is a view, partially in vertical section, of a metal petal basket which is used as an alternative sealing means for the annular air conduit between the combustion tube and the well tubing.

Referring -to FIGURES 1 and 2, a bore hole 10 penetrating an underground rock for-mation 11 is shown having a string of steel casing'13 secured to the wall of the bore hole 10 by a cement sheath 12. Casing 13 and cement sheath 12 are perforated at 14 to permit fluid communication between the formation 11 and the casing 13. vA string of well tubing 15 is supported in the casing 13 from a well head (not shown in the d-rawing) at the surface. Tubing 15 extends downwardly within the cas'- ing 13 to `a depth preferably just above the highest of perforar-tions 14 in casing 13.

A down-hole burner apparatus, indicated generally by the numeral 16, is suspended within tubing 15 substantially near the lower end of tubing 15. A flexible metallic fuel tubing 17 is supported from the well head (not shown) within tubing 15. The bottom of fuel tubing 17 is connected .to a Y-block 18 having `at its upper end an inlet passage 18a which branches to form fuel passage 18b and a thermocouple passage 18C at the lower end of Y-block 18. A sinker bar 19, connected to the bottom of Y-block 18, has a central passage which communicates with fuel passage 18h in Y-block 18. The lower end of sinker bar 19 is connected to a fuel Ifilter 20. Fuel filter 20 forms a fuel filtering chamber 30 containing -a filtering'screen 31.

A back pressure valve 21 is connected to the bottom of f-uel filter 20 and contains a disc 32 which is upwardly biased into closed posi-tion by a spring 33. Disc 32 seats within back pressure valve 21 to provide a fluid tight seal preventing passage of fluid through back pressure valve 21 until the downward force exerted by fiuid pressure upon disc 32 exceeds the upward force exerted upon disc 32 by spring 33.

A combustion tube 22, forming a substantially cylindrical combustion chamber 35, is connected to the b'ottom of back pressure valve 21 and has inwardly extending shoulders forming a closure 44 at its upper end. -Sweep holes 34 extend downwardly into combustion chamber 35 :through the closure 44 Iat the upper end of combustion tube 22. A flame anch'or 36 is suspended within combustion chamber 35 from the lower end of a .fuel line opening into the combustion tube 22. Flame anchor 36 is sealed at its lower end -by plate 37 `and has quadrangular ports 38 extending through -its wall.

Tangential slots 39 extend through the wall of combustion tube 22 and open tangentially 'into combustion chamber 35. As indicated in FIGURE 3, all of tangential slots 39 extend through the wall of combustion tube 22 in the same direction, that is, either clockwise or counterclockwise.

' A tubing stop adapter 23 is connected to the lower end of combustion tube 22 and engages a seating surface 46 in a tubing stop 24 secured to the lower end of well tubing 15, thereby providing a barrier to fluid flow at the lower end of .an annular air conduit 26 formed between the burner apparatus 16 and the well tubing 15. Centrally located vertical passages through the tubing stop adapter 23 and tubing stop 24 provide an exhaust gas conduit 25 for exhaust gases flowing from combustion tube 22 into casing 13 .and through casing perforations 14 into formation 11.

Thermocouple leads are run through fuel tubing 17 and pass through thermocouple conduit 1de of Y-block 18. A flexible thermocouple nipple 27, extending from the bottom of Y-block 18, forms a continuation of thermocouple conduit 18e. The lower end of thermocouple nipple 27 is connected by a tubing connector 28 to a thermocouple tubing 29 extending downwardly outside of the burner apparatus 16 within air conduit 26 to a point near the bottom of combustion tube 22 where thermocouple tubing 29 enters combustion tube 22. The continuous thermocouple leads pass from conduit 13C of Y-block 18 through thermocouple nipple 27 into thermocouple tubing 29 and therethrough downwardly outside combustion tube 22 to form a thermocouple junction within the sealed lower end of thermocouple tubing 29 extending into combustion tube 22. The thermocouple junction and leads are connected to temperature recording means at the surface (not shown in the drawings) and thereby produce a record of the temperature near the bottom of combustion tube 22, which temperature is substantial-ly indicative of the temperature of the hot combustion gases entering the well bore.

In lieu of tubing stop adapter 23 and tubing stop 24, the sealing means for air conduit 26 can comprise a metal petal basket, indicated generally in FIGURE 4 by reference numeral 40. The metal petal basket 4) is secured to combustion tube 22 by shear pin 41. The top of the metal petal basket 40 comprises a plurality of metal petals 42 extending upwardly in air conduit 26 and pressing outwardly against the wall of well tubing to form a fluid barrier in air conduit 26. The construction of the metal petal basket 40 is such that burner apparatus 16 may be inserted in, or removed from, tubing 15 without removing tubing 15 from the bore hole 10. If the progress of the metal petal basket 40 through well tubing 15 is obstructed as the burner apparatus 16 is being inserted in or removed from tubing 15, an upward force applied to the burner apparatus 16 ruptures the shear pin 41 and permits the removal of burner apparatus 16 from tubing 15.

The `assembly and .operation of the burner apparatus can be explained in conjunction with its use in an oil well as depicted in the drawings. The fuel tubing is wound on a spool at the surface and attached to the rest of the burner apparatus at the Y-block. As the burner is lowered in the bore hole the weight of the burner apparatus, augmented by the weight of the sinker bar, unwinds the fuel .tubing from the spool. After the burner apparatus is positioned in the bore hole, separate metered volumes of air are injected into the tubing 15 and casing 13. The fuel tubing is filled with fuel to the surface and a pyrophoric i igniter fluid, such as triethylborane, is inserted in the fuel line above the fuel. Then a metered amount of Huid fuel is pumped into the fuel line above the pyrophoric liquid and under the pressure adequate to open valve 21 and displace the fuel and the pyrophoric liquid through the fuel line. The pyrophoric liquid and the fuel impinge on the base plate of the flame anchor in the presence of the downwardly flowing air stream admitted through the sweep holes through the upper end of the combustion tube. At this point, the pyrophoric liquid ignites in the injected air and ignites the fuel.

Combustion of the fuel-air mixture in the combustion chamber below the flame anchor is supported by continued injection of .air into the annular air conduit between the burner apparatus and the well tubing and through the tangential slots into the combustion chamber. The entry of air through the tangential slots creates a vortex for mixing the fuel and air streams, and the air stream entering through the sweep holes moves the mixture downwardly through the combustion chamber. The downwardly moving vortex of fluids cools the wall of the combustion tube and provides sufficient mixing of the fuel and air to sustain a stable combustion zone with-in the center of the vortex and maintain a constant rate of heat release. v

Various devices such as electrical igniters, Fusee ares and hot charcoal have been suggested for use in down hole heating devices and have been found to be unsatisfactory because they are unreliable at elevated pressures. The use of a pyrophoric liquid with the ame anchor in the burned of this invention provides a reliable means of ignition which is susceptible to a high degree of control by the operator. Triethylborane is a preferred pyrophoric liquid for use with the burner because it does not react with water or hydrocarbons and ignites on contact with air at temperatures equal to or greater than 4 F. Triethylborane ignites spontaneously in air even when mixed with hydrocarbons to as much as 75 percent hydrocarbon contamination. v

Most fluid fuels are suitable for use with the down hole burner of this invention. Preferred fuels are the parain hydrocarbons more volatile than gasoline'such as propane, hexane and heptane. For example, a one inch diameter burner has been operated for extended periods of ltime at a fuel rate of 6.5 gal./hr. of hexane yielding a heat output of 750,000 B.t.u./hr. Suitable air rates in the burner are dependent upon the fuel rate, `and the air rate has between varied from 36 s.c.f./min. to 1000 s.c.f./min. without noticeable effect upon burner performance.

The combination of vertical sweep holes and tangential slots in the combustion tube provides a down hole burner apparatus capable of sustaining stable combination and constant high rates of heat release at high pressures in a conned space. At pressures ranging from atmospheric to 5000 p.s.i.g., a burner having a 11/2 inch diameter combustion tube has been operated continuously for periods `of over 150 hours at temperatures ranging from 360 F. to 3800 F. To avoid damage to the wel-l apparatus, it is ydesirable to restrict the combustion zone substantially within the combustion tube. The use of a metal petal basket or a tubing stop with its adapter to seal the annular air conduit between the burner apparatus and the well tubing causes substantially all of the injected air to flow through the combustion tube and restricts the combustion zone to an interval extending about 6 inches below the bottom of the combustion tube.

A specific embodiment of the down hole burner apparatus of this invention was assembled for use in conventional 21/2 inch oil Well tubing. The fuel line consists of 1A inch Monel tubing, and the thermocouple nipple and thermocouple tubing are made of 1A inch stainless steel tubing. The fuel filter comprises a 1% inch diameter stainless steel tubing, approximately 11A. feet long, containing a mesh stainless steel filtering screen. The combustion tube consists of `a 1'1/2 inch diameter stainless steel tube 24 inches long and contains a flame anchor consisting of a flared pipe coupling of cold rolled steel which is perforated by quadrangular slots and closed at its lower end. Four sweep holes extending into the combustion chamber are spaced evenly around the top of the combustion tube. Near the upper end of the combustion tube, approximately three inches below the bottom of the flame anchor, two rows of rectangular tangenital slots extend through the wall of the combustion tube. Each row contains four slots; each three inches long and evenly spaced around the circumference of the combustion tube.

The improved down hole burner for fluid fuels described in this application f-or Letters Patent is simple to fabricate, install and control. It is capable of continuous controlled operation over a wide range of fuel rates, air rates, temperatures and pressures. Because of its relatively compact construction, the burner can be used in conjunction with conventional oil eld tubular goods.

Therefore I claim:

1. A burner for installation within a tubing string extending down the bore hole of a well for burning therein fluid fuel in oxygen-containing gas supplied to the tubing, said burner comprising a combustion tube within the tubing string having an outer diameter less than the inner diameter of the tubing string to form an annulus between said combustion tube and the tubing string, a closure across the upper end of the combustion tube, a fuel line extending through the closure and opening within the combustion tube, passages extending through said closure for the delivery of air into the combustion tube, slots extending through the wall of the combustion tube and opening substantially tangentially into the combustion tube in a single direction and, sealing means engaging the combustion tube and the tubing string below the slots to close the annulus between the tubing string and the combustion tube.

2. Apparatus for burning a fluid fuel in oxygen-containing gas introduced into the bore hole of a well comprising a tubing string extending down the well, a combustion tube positioned within the tubing string near the lower end thereof, said combustion tube having an outer diameter less than the inner diameter of the tubing string to define therewith an annulus surrounding the combustion tube, a closure at the upper end of the combustion tube, a fuel line extending through the closure and opening within the combustion tube, air passages extending downwardly through the closure, slots extending in a single direction through the walls of the combustion tube and opening substantially tangentially within the combustion tube, and means engaging the tubing string and the outer surface of the combustion tube below the slots to close the annulus around the combustion tube.

3. A burner for installation within a tubing string extending down a well comprising a combustion tube having an outer diameter less than the inner diameter of the tubing string to dene therewith an annulus surrounding the combustion tube, a closure member at the upper end of the combustion tube, a fuel line extending through the closure member and opening within the combustion tube below the lower surface of the closure member, air passages extending downwardly through the closure member, a plurality of slots extending substantially tangentially and in the same direction through the wall of the combustion tube, said slots being positioned below the opening of the fuel line within the combustion tube, and sealing means engaging the tubing string and the combustion tube below the slots to close the lower end of the annulus surrounding the combustion tube.

4. A burner for installation within a tubing string extending down a well comprising a combustion tube having an outer diameter less than the inner diameter of the tubing string to define therewith an annulus surrounding the combustion tube, a closure member at the upper end of the combustion tube, a fuel line extending through the closure member and opening within the combustion tube below the lower surface of the closure member, air passages extending downwardly through the closure member, a plurality of slots extending substantially tangentially'and in the same direction through the wall of the combustion tube, said slots being positioned below the opening of the fuel line within the combustion tube, and sealing means mounted on the combustion tube below the slots adapted to slidably engage the tubing string to close the annulus around the combustion tube.

5. In a burner for fluid fuels for use in the bore hole of .a well having an air conduit extending down said well, the improvement comprising a fuel line extending downwardly within the air conduit, a combustion tube suspended within the air conduit by said fuel line, said combustion tube having an outer diameter less than the inner diameter of the air conduit to define therewith an annulus surrounding said combustion tube, a closure member across the upper end of the combustion tube, said fuel line extending through said closure member and opening within the combustion tube, a plurality of passages extending downwardly through said closure member to allow ow from the air conduit into the combustion tube, slots extending in a single direction substantially tangentially through the wall of the combustion tube, and sealing means on the combustion tube adapted to engage the air conduit to close the annulus surrounding the combus- -6 tion tube upon lowering Ithe combustion tube through the air conduit to a desired position therein.

6. Apparatus as set forth in claim 5 in which the fuel line extends through the combustion tube and opens therein at a position spaced below the closure member, and a flame anchor is suspended within the combustion tube below the opening of the fuel line therein..

7. In apparatus for burning a `fluid fuel inthe bore hole of a well having an air conduit extending from the surface down the well, the improvement comprising a fuel line extending down the air conduit, a combustion tube suspended within the air conduit by the fuel line, said combustion tube forming a combustion chamber, closure means at the upper end of the combustion tube, said fuel line extending through said closure means and opening within the combustion chamber at a position spaced below the lower surface of the closure means, passages extending downwardly through the closure means for allowing flow from the airconduit into the combustion chamber, a plurality of slots extending through the wall of the combustion tube and opening substantially tangentially in the same direction into the combustion chamber, said slots being located below the outlet of the fuel line within the combustion chamber, and sealing means adapted t0 engage the combustion tube and the air conduit to close the annulus therebetween.

8. In apparatus for burning a fluid fuel in the bore hole of a well having an air conduit extending from the surface down the well, the improvement comprising a fuel line extending down the air conduit, a combustion tube suspended within the air conduit by the fuel line, Vsaid combustion tube forming a combustion chamber, closure means in the upper end of the combustion tube, said fuel line extending through said closuremeans and opening within the combustion chamber at a position spaced below the lower surface of the closure means, passages eX- tending downwardly through the closure means for allowing flow from the air conduit into the combustion chamber, a plurality of slots extending through the wall of the combustion tube and opening substantially tangentially in the same direction into the combustion chamber, said slots being located below the outlet of the fuel line within the combustion chamber, a collar mounted on said air conduit and extending inwardly therefrom, an Iupwardly opening seating surface on said collar, and means at the lower end of said combustion tube adapted to engage the seating surface and close the lower end of the annulus between the combustion tube and the 'air conduit.

9. In apparatus for burning a fluid fuel in the bore hole of a Well having an air conduit extending from the surface down the well, the improvement comprising a fuel line extending down the air conduit, a combustion tube suspended within the air conduit by the fuel line, said combustion tube forming a combustion chamber, closure means at the upper end of the combustion tube, said fuel line extending through said closure means and opening within the combustion chamber at a position spaced below the lower surface of the closure means, passages extending downwardly through the closure means for allowing ilow from the air conduit into the combustion chamber, a plurality of slots extending through the wall of the combustion tube and opening substantially tangentially in the same direction into the combustion chamber, said slots being located below the outlet of the fuel line within the combustion chamber, and a metal petal basket mounted below the slots on said combustion tube and adapted to slidably engage the air conduit, and close the annulus between the combustion tube and the air conduit.

10. Apparatus for burning a fluid fuel within a tubing string extending down the bore hole of a well comprising a combustion tube positioned within the tubing string, said combustion tube having an outer diameter smaller than the inner diameter of the tubing string to dene therewith an annulus surrounding the combustion tube, a closure member at the upper end of the combustion tube, a fuel line engaging and extending through the closure member to suspend the combustion tube Within the tubing string.` said fuel line opening within the combustion tube at a position spaced below the closure member, a valve springbiased upwardly to a closed position in said fuel line above the combustion tube, air passages extending through the closure member to allow flow from within the tubing string into the combustion tube, a plurality of slots extending substantially tangentially in a single direction through the wall of the combustion tube, and means engaging the combustion tube and the tubing string to close the annulus surrounding the combustion tube at a level below the slots.

11. Apparatus for burning a Huid fuel within a tubing string extending down the bore hole of a well comprising a combustion tube positioned within the tubing string, said combustion tube having an outer diameter smaller than the inner diameter of the tubing string to dene therewith an annulus surrounding the combustion tube, a closure member at the upper end of the combustion tube, a fuel line engaging and extending through the closure member to suspend the combustion tube within the tubing string, said fuel line opening within the combustion tube at a 4position spaced below the closure member, filter means in and forming a part of the fuel line, a valve springbiased upwardly to a closed position in said fuel line above the combustion tube, air passages extending through the closure member to allow flow from within the tubing string into the combustion tube, a plurality of slots extending substantially tangentially in a single direction through the wall of the combustion tube, and means engaging the combustion tube and the tubing string to close the annulus surrounding the combustion tube at a level below the slots.

12. vA burner for combustion of Huid fuel in oxygencontaining gas introduced into a tubing string extending down the borehole of a well, said burner comprising a combustion tube within the tubing string forming an annulus therewith, said combustion tube being open at its lower end for the discharge of combustion products therefrom, a closure at the upper end of the combustion tube, a fuel line extending through the `closure and opening within the combustion tube, first air passages extending through the closure to deliver airsubstantially longitudinally through the combustion tube, second air passages extending tangentially and undirectionally through the Wall of the combustion tube to deliver a vortical stream of air into the combustion tube, and sealing means engaging the combustion tube and tubing string below the second air passages to close the annulus.

References Cited bythe Examiner Emery 166-59 CHARLES E. OCONNELL, Primary Examiner.

D. H. BROWN, Assistant Examiner. 

3. A BURNER FOR INSTALLATION WITHIN A TUBING STRING EXTENDING DOWN A WELL COMPRISING A COMBUSTION TUBE HAVING AN OUTER DIAMETER LESS THAN THE INNER DIAMETER OF THE TUBING STRING TO DEFINE THEREWITH AN ANNULUS SURROUNDING THE COMBUSTION TUBE, A CLOSURE MEMBER AT THE UPPER END OF THE COMBUSTION TUBE, A FUEL LINE EXTENDING THROUGH THE CLOSURE MEMBER AND OPENING WITHIN THE COMBUSTION TUBE BELOW THE LOWER SURFACE OF THE CLOSURE MEMBER, AIR PASSAGES EXTENDING DOWNWARDLY THROUGH THE CLOSURE MEMBER, A PLURALITY OF SLOTS EXTENDING SUBSTANTIALLY TANGENTIALLY AND IN THE SAME DIRECTION THROUGH THE WALL OF THE COMBUSTION TUBE, SAID SLOTS BEING POSITIONED BELOW THE OPENING OF THE FUEL LINE WITHIN THE COMBUSTION TUBE, AND 